Inbred maize line PHDN7

ABSTRACT

An inbred maize line, designated PHDN7, the plants and seeds of inbred maize line PHDN7, methods for producing a maize plant produced by crossing the inbred line PHDN7 with itself or with another maize plant, and hybrid maize seeds and plants produced by crossing the inbred line PHDN7 with another maize line or plant.

FIELD OF THE INVENTION

This invention is in the field of maize breeding, specifically relating to an inbred maize line designated PHDN7.

BACKGROUND OF THE INVENTION

The goal of plant breeding is to combine in a single variety or hybrid various desirable traits. For field crops, these traits may include resistance to diseases and insects, tolerance to heat and drought, reducing the time to crop maturity, greater yield, and better agronomic quality. With mechanical harvesting of many crops, uniformity of plant characteristics such as germination and stand establishment, growth rate, maturity, and plant and ear height, is important.

Field crops are bred through techniques that take advantage of the plant's method of pollination. A plant is self-pollinated if pollen from one flower is transferred to the same or another flower of the same plant. A plant is cross-pollinated if the pollen comes from a flower on a different plant.

Plants that have been self-pollinated and selected for type for many generations become homozygous at almost all gene loci and produce a uniform population of true breeding progeny. A cross between two different homozygous lines produces a uniform population of hybrid plants that may be heterozygous for many gene loci. A cross of two plants each heterozygous at a number of gene loci will produce a population of hybrid plants that differ genetically and will not be uniform.

Maize (Zea mays L.), often referred to as corn in the United States, can be bred by both self-pollination and cross-pollination techniques. Maize has separate male and female flowers on the same plant, located on the tassel and the ear, respectively. Natural pollination occurs in maize when wind blows pollen from the tassels to the silks that protrude from the tops of the ears.

A reliable method of controlling male fertility in plants offers the opportunity for improved plant breeding. This is especially true for development of maize hybrids, which relies upon some sort of male sterility system. There are several options for controlling male fertility available to breeders, such as: manual or mechanical emasculation (or detasseling), cytoplasmic male sterility, genetic male sterility, gametocides and the like.

Hybrid maize seed is typically produced by a male sterility system incorporating manual or mechanical detasseling. Alternate strips of two maize inbreds are planted in a field, and the pollen-bearing tassels are removed from one of the inbreds (female). Providing that there is sufficient isolation from sources of foreign maize pollen, the ears of the detasseled inbred will be fertilized only from the other inbred (male), and the resulting seed is therefore hybrid and will form hybrid plants.

The laborious, and occasionally unreliable, detasseling process can be avoided by using cytoplasmic male-sterile (CMS) inbreds. Plants of a CMS inbred are male sterile as a result of factors resulting from the cytoplasmic, as opposed to the nuclear, genome. Thus, this characteristic is inherited exclusively through the female parent in maize plants, since only the female provides cytoplasm to the fertilized seed. CMS plants are fertilized with pollen from another inbred that is not male-sterile. Pollen from the second inbred may or may not contribute genes that make the hybrid plants male-fertile. Seed from detasseled fertile maize and CMS produced seed of the same hybrid can be blended to insure that adequate pollen loads are available for fertilization when the hybrid plants are grown.

There are several methods of conferring genetic male sterility available, such as multiple mutant genes at separate locations within the genome that confer male sterility, as disclosed in U.S. Pat. Nos. 4,654,465 and 4,727,219 to Brar et al. and chromosomal translocations as described by Patterson in U.S. Pat. Nos. 3,861,709 and 3,710,511. These and all patents referred to are incorporated by reference. In addition to these methods, Albertsen et al., of Pioneer Hi-Bred, U.S. patent application Ser. No. 07/848,433, have developed a system of nuclear male sterility which includes: identifying a gene which is critical to male fertility; silencing this native gene which is critical to male fertility; removing the native promoter from the essential male fertility gene and replacing it with an inducible promoter; inserting this genetically engineered gene back into the plant; and thus creating a plant that is male sterile because the inducible promoter is not "on" resulting in the male fertility gene not being transcribed. Fertility is restored by inducing, or turning "on", the promoter, which in turn allows the gene that confers male fertility to be transcribed.

There are many other methods of conferring genetic male sterility in the art, each with its own benefits and drawbacks. These methods use a variety of approaches such as delivering into the plant a gene encoding a cytotoxic substance associated with a male tissue specific promoter or an antisense system in which a gene critical to fertility is identified and an antisense to that gene is inserted in the plant (see: Fabinjanski, et al. EPO 89/3010153.8 publication no. 329,308 and PCT application PCT/CA90/00037 published as WO 90/08828).

Another system useful in controlling male sterility makes use of gametocides. Gametocides are not a genetic system, but rather a topical application of chemicals. These chemicals affect cells that are critical to male fertility. The application of these chemicals affects fertility in the plants only for the growing season in which the gametocide is applied (see Carlson, Glenn R., U.S. Pat. No. 4,936,904). Application of the gametocide, timing of the application and genotype specificity often limit the usefulness of the approach.

The use of male sterile inbreds is but one factor in the production of maize hybrids. The development of maize hybrids requires, in general, the development of homozygous inbred lines, the crossing of these lines, and the evaluation of the crosses. Pedigree breeding and recurrent selection breeding methods are used to develop inbred lines from breeding populations. Breeding programs combine the genetic backgrounds from two or more inbred lines or various other germplasm sources into breeding pools from which new inbred lines are developed by selfing and selection of desired phenotypes. The new inbreds are crossed with other inbred lines and the hybrids from these crosses are evaluated to determine which of those have commercial potential. Plant breeding and hybrid development are expensive and time consuming processes.

Pedigree breeding starts with the crossing of two genotypes, each of which may have one or more desirable characteristics that is lacking in the other or which complements the other. If the two original parents do not provide all the desired characteristics, other sources can be included in the breeding population. In the pedigree method, superior plants are selfed and selected in successive generations. In the succeeding generations the heterozygous condition gives way to homogeneous lines as a result of self-pollination and selection. Typically in the pedigree method of breeding five or more generations of selfing and selection is practiced: F₁ →F₂ ; F₃ →F₄ ; F₄ →F₅, etc.

Recurrent selection breeding, backcrossing for example, can be used to improve an inbred line. Backcrossing can be used to transfer a specific desirable trait from one inbred or source to an inbred that lacks that trait. This can be accomplished, for example, by first crossing a superior inbred (recurrent parent) to a donor inbred (non-recurrent parent), that carries the appropriate gene(s) for the trait in question. The progeny of this cross is then mated back to the superior recurrent parent followed by selection in the resultant progeny for the desired trait to be transferred from the non-recurrent parent. After five or more backcross generations with selection for the desired trait, the progeny will be heterozygous for loci controlling the characteristic being transferred, but will be like the superior parent for most or almost all other genes. The last backcross generation is then selfed to give pure breeding progeny for the gene(s) being transferred.

A single cross maize hybrid results from the cross of two inbred lines, each of which has a genotype that complements the genotype of the other. The hybrid progeny of the first generation is designated F₁. In the development of commercial hybrids only the F₁ hybrid plants are sought. Preferred F₁ hybrids are more vigorous than their inbred parents. This hybrid vigor, or heterosis, can be manifested in many polygenic traits, including increased vegetative growth and increased yield.

The development of a maize hybrid involves three steps: (1) the selection of plants from various germplasm pools for initial breeding crosses; (2) the selfing of the selected plants from the breeding crosses for several generations to produce a series of inbred lines, which, although different from each other, breed true and are highly uniform; and (3) crossing the selected inbred lines with different inbred lines to produce the hybrid progeny (F₁). During the inbreeding process in maize, the vigor of the lines decreases. Vigor is restored when two different inbred lines are crossed to produce the hybrid progeny (F₁). An important consequence of the homozygosity and homogeneity of the inbred lines is that the hybrid between a defined pair of inbreds will always be the same. Once the inbreds that give a superior hybrid have been identified, the hybrid seed can be reproduced indefinitely as long as the homogeneity of the inbred parents is maintained.

A single cross hybrid is produced when two inbred lines are crossed to produce the F₁ progeny. A double cross hybrid is produced from four inbred lines crossed in pairs (A×B and C×D) and then the two F₁ hybrids are crossed again (A×B)×(C×D). Much of the hybrid vigor exhibited by F₁ hybrids is lost in the next generation (F₂). Consequently, seed from hybrids is not used for planting stock.

Hybrid seed production requires elimination or inactivation of pollen produced by the female parent. Incomplete removal or inactivation of the pollen provides the potential for self pollination. This inadvertently self pollinated seed may be unintentionally harvested and packaged with hybrid seed.

Once the seed is planted, it is possible to identify and select these self pollinated plants. These self pollinated plants will be genetically equivalent to the female inbred line used to produce the hybrid.

Typically these self pollinated plants can be identified and selected due to their decreased vigor. Female selfs are identified by their less vigorous appearance for vegetative and/or reproductive characteristics, including shorter plant height, small ear size, ear and kernel shape, cob color, or other characteristics.

Identification of these self pollinated lines can also be accomplished through molecular marker analyses. See, "The Identification of Female Selfs in Hybrid Maize: A Comparison Using Electrophoresis and Morphology", Smith, J. S. C. and Wych, R. D., Seed Science and Technology 14, pp. 1-8 (1995), the disclosure of which is expressly incorporated herein by reference. Through these technologies, the homozygosity of the self pollinated line can be verified by analyzing allelic composition at various loci along the genome. Those methods allow for rapid identification of the invention disclosed herein. See also, "Identification of Atypical Plants in Hybrid Maize Seed by Postcontrol and Electrophoresis" Sarca, V. et al., Probleme de Genetica Teoritica si Aplicata Vol. 20 (1) p. 29-42.

As is readily apparent to one skilled in the art, the foregoing are only two of the various ways by which the inbred can be obtained by those looking to use the germplasm. Other means are available, and the above examples are illustrative only.

Maize is an important and valuable field crop. Thus, a continuing goal of plant breeders is to develop high-yielding maize hybrids that are agronomically sound based on stable inbred lines. The reasons for this goal are obvious: to maximize the amount of grain produced with the inputs used and minimize susceptibility of the crop to pests and environmental stresses. To accomplish this goal, the maize breeder must select and develop superior inbred parental lines for producing hybrids. This requires identification and selection of genetically unique individuals that occur in a segregating population. The segregating population is the result of a combination of crossover events plus the independent assortment of specific combinations of alleles at many gene loci that results in specific genotypes. The probability of selecting any one individual with a specific genotype from a breeding cross is infinitesimal due to the large number of segregating genes and the unlimited recombinations of these genes, some of which may be closely linked. However, the genetic variation among individual progeny of a breeding cross allows for the identification of rare and valuable new genotypes. These new genotypes are neither predictable nor incremental in value, but rather the result of manifested genetic variation combined with selection methods, environments and the actions of the breeder.

Thus, even if the entire genotypes of the parents of the breeding cross were characterized and a desired genotype known, only a few, if any, individuals having the desired genotype may be found in a large segregating F₂ population. Typically, however, neither the genotypes of the breeding cross parents nor the desired genotype to be selected is known in any detail. In addition, it is not known how the desired genotype would react with the environment. This genotype by environment interaction is an important, yet unpredictable, factor in plant breeding. A breeder of ordinary skill in the art cannot predict the genotype, how that genotype will interact with various climatic conditions or the resulting phenotypes of the developing lines, except perhaps in a very broad and general fashion. A breeder of ordinary skill in the art would also be unable to recreate the same line twice from the very same original parents as the breeder is unable to direct how the genomes combine or how they will interact with the environmental conditions. This unpredictability results in the expenditure of large amounts of research resources in the development of a superior new maize inbred line.

SUMMARY OF THE INVENTION

According to the invention, there is provided a novel inbred maize line, designated PHDN7. This invention thus relates to the seeds of inbred maize line PHDN7, to the plants of inbred maize line PHDN7, and to methods for producing a maize plant produced by crossing the inbred line PHDN7 with itself or another maize line. This invention further relates to hybrid maize seeds and plants produced by crossing the inbred line PHDN7 with another maize line.

DEFINITIONS

In the description and examples that follow, a number of terms are used herein. In order to provide a clear and consistent understanding of the specification and claims, including the scope to be given such terms, the following definitions are provided. NOTE: ABS is in absolute terms and % MN is percent of the mean for the experiments in which the inbred or hybrid was grown. These designators will follow the descriptors to denote how the values are to be interpreted. Below are the descriptors used in the data tables included herein.

ANT ROT=ANTHRACNOSE STALK ROT (Colletotrichum graminicola). A 1 to 9 visual rating indicating the resistance to Anthracnose Stalk Rot. A higher score indicates a higher resistance.

BAR PLT=BARREN PLANTS. The percent of plants per plot that were not barren (lack ears).

BRT STK=BRITTLE STALKS. This is a measure of the stalk breakage near the time of pollination, and is an indication of whether a hybrid or inbred would snap or break near the time of flowering under severe winds. Data are presented as percentage of plants that did not snap.

BU ACR=YIELD (BUSHELS/ACRE). Yield of the grain at harvest in bushels per acre adjusted to 15.5% moisture.

CLD TST=COLD TEST. The percent of plants that germinate under cold test conditions.

CLN=CORN LETHAL NECROSIS. Synergistic interaction of maize chlorotic mottle virus (MCMV) in combination with either maize dwarf mosaic virus (MDMV-A or MDMV-B) or wheat streak mosaic virus (WSMV). A 1 to 9 visual rating indicating the resistance to Corn Lethal Necrosis. A higher score indicates a higher resistance.

COM RST=COMMON RUST (Puccinia sorghi). A 1 to 9 visual rating indicating the resistance to Common Rust. A higher score indicates a higher resistance.

D/D=DRYDOWN. This represents the relative rate at which a hybrid will reach acceptable harvest moisture compared to other hybrids on a 1-9 rating scale. A high score indicates a hybrid that dries relatively fast while a low score indicates a hybrid that dries slowly.

DIP ERS=DIPLODIA EAR MOLD SCORES (Diplodia maydis and Diplodia macrospora). A 1 to 9 visual rating indicating the resistance to Diplodia Ear Mold. A higher score indicates a higher resistance.

DRP EAR=DROPPED EARS. A measure of the number of dropped ears per plot and represents the percentage of plants that did not drop ears prior to harvest.

D/T=DROUGHT TOLERANCE. This represents a 1-9 rating for drought tolerance, and is based on data obtained under stress conditions. A high score indicates good drought tolerance and a low score indicates poor drought tolerance.

EAR HT=EAR HEIGHT. The ear height is a measure from the ground to the highest placed developed ear node attachment and is measured in inches.

EAR MLD=General Ear Mold. Visual rating (1-9 score) where a "1" is very susceptible and a "9" is very resistant. This is based on overall rating for ear mold of mature ears without determining the specific mold organism, and may not be predictive for a specific ear mold.

EAR SZ=EAR SIZE. A 1 to 9 visual rating of ear size. The higher the rating the larger the ear size.

ECB 1LF=EUROPEAN CORN BORER FIRST GENERATION LEAF FEEDING (Ostrinia nubilalis). A 1 to 9 visual rating indicating the resistance to preflowering leaf feeding by first generation European Corn Borer. A higher score indicates a higher resistance.

ECB 2IT=EUROPEAN CORN BORER SECOND GENERATION INCHES OF TUNNELING (Ostrinia nubilalis). Average inches of tunneling per plant in the stalk.

ECB 2SC=EUROPEAN CORN BORER SECOND GENERATION (Ostrinia nubilalis). A 1 to 9 visual rating indicating post flowering degree of stalk breakage and other evidence of feeding by European Corn Borer, Second Generation. A higher score indicates a higher resistance.

ECB DPE=EUROPEAN CORN BORER DROPPED EARS (Ostrinia nubilalis). Dropped ears due to European Corn Borer. Percentage of plants that did not drop ears under second generation corn borer infestation.

EST CNT=EARLY STAND COUNT. This is a measure of the stand establishment in the spring and represents the number of plants that emerge on per plot basis for the inbred or hybrid.

EYE SPT=Eye Spot (Kabatiella zeae or Aureobasidium zeae). A 1 to 9 visual rating indicating the resistance to Eye Spot. A higher score indicates a higher resistance.

FUS ERS=FUSARIUM EAR ROT SCORE (Fusarium moniliforme or Fusarium subglutinans). A 1 to 9 visual rating indicating the resistance to Fusarium ear rot. A higher score indicates a higher resistance.

GDU=Growing Degree Units. Using the Barger Heat Unit Theory, which assumes that maize growth occurs in the temperature range 50° F.-86° F. and that temperatures outside this range slow down growth; the maximum daily heat unit accumulation is 36 and the minimum daily heat unit accumulation is 0. The seasonal accumulation of GDU is a major factor in determining maturity zones.

GDU SHD=GDU TO SHED. The number of growing degree units (GDUs) or heat units required for an inbred line or hybrid to have approximately 50 percent of the plants shedding pollen and is measured from the time of planting. Growing degree units are calculated by the Barger Method, where the heat units for a 24-hour period are: ##EQU1##

The highest maximum temperature used is 86° F. and the lowest minimum temperature used is 50° F. For each inbred or hybrid it takes a certain number of GDUs to reach various stages of plant development.

GDU SLK=GDU TO SILK. The number of growing degree units required for an inbred line or hybrid to have approximately 50 percent of the plants with silk emergence from time of planting. Growing degree units are calculated by the Barger Method as given in GDU SHD definition.

GIB ERS=GIBBERELLA EAR ROT (PINK MOLD) (Gibberella zeae). A 1 to 9 visual rating indicating the resistance to Gibberella Ear Rot. A higher score indicates a higher resistance.

GLF SPT=Gray Leaf Spot (Cercospora zeae-maydis). A 1 to 9 visual rating indicating the resistance to Gray Leaf Spot. A higher score indicates a higher resistance.

GOS WLT=Goss' Wilt (Corynebacterium nebraskense). A 1 to 9 visual rating indicating the resistance to Goss' Wilt. A higher score indicates a higher resistance.

GRN APP=GRAIN APPEARANCE. This is a 1 to 9 rating for the general appearance of the shelled grain as it is harvested based on such factors as the color of harvested grain, any mold on the grain, and any cracked grain. High scores indicate good grain quality.

H/POP=YIELD AT HIGH DENSITY. Yield ability at relatively high plant densities on 1-9 relative rating system with a higher number indicating the hybrid responds well to high plant densities for yield relative to other hybrids. A 1, 5, and 9 would represent very poor, average, and very good yield response, respectively, to increased plant density.

HC BLT=HELMINTHOSPORIUM CARBONUM LEAF BLIGHT (Helminthosporium carbonum). A 1 to 9 visual rating indicating the resistance to Helminthosporium infection. A higher score indicates a higher resistance.

HD SMT=HEAD SMUT (Sphacelotheca reiliana). This score indicates the percentage of plants not infected.

INC D/A=GROSS INCOME (DOLLARS PER ACRE). Relative income per acre assuming drying costs of two cents per point above 15.5 percent harvest moisture and current market price per bushel.

INCOME/ACRE. Income advantage of hybrid to be patented over other hybrid on per acre basis.

INC ADV=GROSS INCOME ADVANTAGE. GROSS INCOME advantage of variety #1 over variety #2.

KSZ DCD=KERNEL SIZE DISCARD. The percent of discard seed; calculated as the sum of discarded tip kernels and extra large kernels.

L/POP=YIELD AT LOW DENSITY. Yield ability at relatively low plant densities on a 1-9 relative system with a higher number indicating the hybrid responds well to low plant densities for yield relative to other hybrids. A 1, 5, and 9 would represent very poor, average, and very good yield response, respectively, to low plant density.

MDM CPX=MAIZE DWARF MOSAIC COMPLEX (MDMV=Maize Dwarf Mosaic Virus and MCDV=Maize Chlorotic Dwarf Virus). A 1 to 9 visual rating indicating the resistance to Maize Dwarf Mosaic Complex. A higher score indicates a higher resistance.

MST=HARVEST MOISTURE. The moisture is the actual percentage moisture of the grain at harvest.

MST ADV=MOISTURE ADVANTAGE. The moisture advantage of variety #1 over variety #2 as calculated by: MOISTURE of variety #2-MOISTURE of variety #1=MOISTURE ADVANTAGE of variety #1.

NLF BLT=Northern Leaf Blight (Helminthosporium turcicum or Exserohilum turcicum). A 1 to 9 visual rating indicating the resistance to Northern Leaf Blight. A higher score indicates a higher resistance.

PLT HT=PLANT HEIGHT. This is a measure of the height of the plant from the ground to the tip of the tassel in inches.

POL SC=POLLEN SCORE. A 1 to 9 visual rating indicating the amount of pollen shed. The higher the score the more pollen shed.

POL WT=POLLEN WEIGHT. This is calculated by dry weight of tassels collected as shedding commences minus dry weight from similar tassels harvested after shedding is complete.

It should be understood that the inbred can, through routine manipulation of cytoplasmic or other factors, be produced in a male-sterile form. Such embodiments are also contemplated within the scope of the present claims.

POP K/A=PLANT POPULATIONS. Measured as 1000s per acre.

POP ADV=PLANT POPULATION ADVANTAGE. The plant population advantage of variety #1 over variety #2 as calculated by PLANT POPULATION of variety #2-PLANT POPULATION of variety #1=PLANT POPULATION ADVANTAGE of variety #1.

PRM=PREDICTED RELATIVE MATURITY. This trait, predicted relative maturity, is based on the harvest moisture of the grain. The relative maturity rating is based on a known set of checks and utilizes standard linear regression analyses and is also referred to as the Comparative Relative Maturity Rating System that is similar to the Minnesota Relative Maturity Rating System.

PRM SHD=A relative measure of the growing degree units (GDU) required to reach 50% pollen shed. Relative values are predicted values from the linear regression of observed GDU's on relative maturity of commercial checks.

RT LDG=ROOT LODGING. Root lodging is the percentage of plants that do not root lodge; plants that lean from the vertical axis at an approximately 30° angle or greater would be counted as root lodged.

RTL ADV=ROOT LODGING ADVANTAGE. The root lodging advantage of variety #1 over variety #2.

SCT GRN=SCATTER GRAIN. A 1 to 9 visual rating indicating the amount of scatter grain (lack of pollination or kernel abortion) on the ear. The higher the score the less scatter grain.

SDG VGR=SEEDLING VIGOR. This is the visual rating (1 to 9) of the amount of vegetative growth after emergence at the seedling stage (approximately five leaves). A higher score indicates better vigor.

SEL IND=SELECTION INDEX. The selection index gives a single measure of the hybrid's worth based on information for up to five traits. A maize breeder may utilize his or her own set of traits for the selection index. One of the traits that is almost always included is yield. The selection index data presented in the tables represent the mean value averaged across testing stations.

SLF BLT=SOUTHERN LEAF BLIGHT (Helminthosporium maydis or Bipolaris maydis). A 1 to 9 visual rating indicating the resistance to Southern Leaf Blight. A higher score indicates a higher resistance.

SOU RST=SOUTHERN RUST (Puccinia polysora). A 1 to 9 visual rating indicating the resistance to Southern Rust. A higher score indicates a higher resistance.

STA GRN=STAY GREEN. Stay green is the measure of plant health near the time of black layer formation (physiological maturity). A high score indicates better late-season plant health.

STD ADV=STALK STANDING ADVANTAGE. The advantage of variety #1 over variety #2 for the trait STK CNT.

STK CNT=NUMBER OF PLANTS. This is the final stand or number of plants per plot.

STK LDG=STALK LODGING. This is the percentage of plants that did not stalk lodge (stalk breakage) as measured by either natural lodging or pushing the stalks and determining the percentage of plants that break below the ear.

STW WLT=Stewart's Wilt (Erwinia stewartii). A 1 to 9 visual rating indicating the resistance to Stewart's Wilt. A higher score indicates a higher resistance.

TAS BLS=TASSEL BLAST. A 1 to 9 visual rating was used to measure the degree of blasting (necrosis due to heat stress) of the tassel at the time of flowering. A 1 would indicate a very high level of blasting at time of flowering, while a 9 would have no tassel blasting.

TAS SZ=TASSEL SIZE. A 1 to 9 visual rating was used to indicate the relative size of the tassel. The higher the rating the larger the tassel.

TAS WT=TASSEL WEIGHT. This is the average weight of a tassel (grams) just prior to pollen shed.

TEX EAR=EAR TEXTURE. A 1 to 9 visual rating was used to indicate the relative hardness (smoothness of crown) of mature grain. A 1 would be very soft (extreme dent) while a 9 would be very hard (flinty or very smooth crown).

TILLER=TILLERS. A count of the number of tillers per plot that could possibly shed pollen was taken. Data are given as a percentage of tillers: number of tillers per plot divided by number of plants per plot.

TST WT=TEST WEIGHT (UNADJUSTED). The measure of the weight of the grain in pounds for a given volume (bushel).

TST WTA=TEST WEIGHT ADJUSTED. The measure of the weight of the grain in pounds for a given volume (bushel) adjusted for 15.5 percent moisture.

TSW ADV=TEST WEIGHT ADVANTAGE. The test weight advantage of variety #1 over variety #2.

WIN M %=PERCENT MOISTURE WINS.

WIN Y %=PERCENT YIELD WINS.

YLD=YIELD. It is the same as BU ACR ABS.

YLD ADV=YIELD ADVANTAGE. The yield advantage of variety #1 over variety #2 as calculated by: YIELD of variety #1-YIELD variety #2=yield advantage of variety #1.

YLD SC=YIELD SCORE. A 1 to 9 visual rating was used to give a relative rating for yield based on plot ear piles. The higher the rating the greater visual yield appearance.

DETAILED DESCRITPION OF THE INVENTION

Inbred maize lines are typically developed for use in the production of hybrid maize lines. Inbred maize lines need to be highly homogeneous, homozygous and reproducible to be useful as parents of commercial hybrids. There are many analytical methods available to determine the homozygotic and phenotypic stability of these inbred lines.

The oldest and most traditional method of analysis is the observation of phenotypic traits. The data is usually collected in field experiments over the life of the maize plants to be examined. Phenotypic characteristics most often observed are for traits associated with plant morphology, ear and kernel morphology, insect and disease resistance, maturity, and yield.

In addition to phenotypic observations, the genotype of a plant can also be examined. There are many laboratory-based techniques available for the analysis, comparison and characterization of plant genotype; among these are Isozyme Electrophoresis, Restriction Fragment Length Polymorphisms (RFLPs), Randomly Amplified Polymorphic DNAs (RAPDs), Arbitrarily Primed Polymerase Chain Reaction (AP-PCR), DNA Amplification Fingerprinting (DAF), Sequence Characterized Amplified Regions (SCARs), Amplified Fragment Length Polymorphisms (AFLPs), and Simple Sequence Repeats (SSRs) which are also referred to as Microsatellites.

The most widely used of these laboratory techniques are Isozyme Electrophoresis and RFLPs as discussed in Lee, M., "Inbred Lines of Maize and Their Molecular Markers," The Maize Handbook, (Springer-Verlag, New York, Inc. 1994, at 423-432) incorporated herein by reference. Isozyme Electrophoresis is a useful tool in determining genetic composition, although it has relatively low number of available markers and the low number of allelic variants among maize inbreds. RFLPs have the advantage of revealing an exceptionally high degree of allelic variation in maize and the number of available markers is almost limitless.

Maize RFLP linkage maps have been rapidly constructed and widely implemented in genetic studies. One such study is described in Boppenmaier, et al., "Comparisons among strains of inbreds for RFLPs", Maize Genetics Cooperative Newsletter, 65:1991, pg. 90, is incorporated herein by reference. This study used 101 RFLP markers to analyze the patterns of 2 to 3 different deposits each of five different inbred lines. The inbred lines had been selfed from 9 to 12 times before being adopted into 2 to 3 different breeding programs. It was results from these 2 to 3 different breeding programs that supplied the different deposits for analysis. These five lines were maintained in the separate breeding programs by selfing or sibbing and rogueing off-type plants for an additional one to eight generations. After the RFLP analysis was completed, it was determined the five lines showed 0-2% residual heterozygosity. Although this was a relatively small study, it can be seen using RFLPs that the lines had been highly homozygous prior to the separate strain maintenance.

Inbred maize line PHDN7 is a yellow, dent maize inbred that is suited as either a male or female in crosses for producing first generation F₁ maize hybrids. Inbred maize line PHDN7 is best adapted to the Northwest, Northcentral and Northeast regions of the United States and the Corn Belt regions of Canada, Austria, Czechia, Slovakia, Hungary, Romania, Slovenia and Croatia and can be used to produce hybrids from approximately 92 relative maturity based on the Comparative Relative Maturity Rating System for harvest moisture of grain. Inbred maize line PHDN7 demonstrates good general combining ability and works well as either a male or a female in crosses. In hybrid combination, PHDN7 demonstrates high yield and early maturity. For its area of adaptation, PHDN7 also demonstrates high yield and early maturity.

The inbred has shown uniformity and stability within the limits of environmental influence for all the traits as described in the Variety Description Information (Table 1) that follows. The inbred has been self-pollinated and ear-rowed a sufficient number of generations with careful attention paid to uniformity of plant type to ensure the homozygosity and phenotypic stability necessary to use in commercial production. The line has been increased both by hand and in isolated fields with continued observation for uniformity. No variant traits have been observed or are expected in PHDN7.

Inbred maize line PHDN7, being substantially homozygous, can be reproduced by planting seeds of the line, growing the resulting maize plants under self-pollinating or sib-pollinating conditions with adequate isolation, and harvesting the resulting seed, using techniques familiar to the agricultural arts.

                                      TABLE 1     __________________________________________________________________________     VARIETY DESCRIPTION INFORMATION     VARIETY = PHDN7     __________________________________________________________________________     1. TYPE: (describe intermediate types in Comments section):     2   1 = Sweet 2 = Dent 3 = Flint 4 = Flour 5 = Pop 6 = Ornamental     2. MATURITY:     DAYS  HEAT UNITS     062   1,230.7                  From emergence to 50% of plants in silk     062   1,240.5                  From emergence to 50% of plants in pollen     006   0,135.2                  From 10% to 90% pollen shed     067   1,341.8                  From 50% silk to harvest at 25% moisture     3. PLANT:                      Standard                                         Sample                                    Deviation                                         Size     0,206.0           cm Plant Height (to tassel tip)                                    22.16                                         6     0,080.5           cm Ear Height (to base of top ear node)                                    11.17                                         6     0,015.4           cm Length of Top Ear Intermode                                    2.25 30     1        Average Number of Tillers                                    0.00 6     1.2      Average Number of Ears per Stalk                                    0.41 6     4.0      Anthocyanin of Brace Roots: 1 = Absent 2 = Faint 3 = Moderate 4              = Dark     4. LEAF:                       Standard                                         Sample                                    Deviation                                         Size     008.1 cm Width of Ear Node Leaf                                    0.85 30     071.5 cm Length of Ear Node Leaf                                    15.15                                         30     05.0     Number of leaves above top ear                                    0.57 30     039.7    Degrees Leaf Angle (measure from 2nd leaf above                                    6.77 6              ear at anthesis to stalk above leaf)     03       Leaf Color Dark Green (Munsell code)                                        5GY 4/6     1.0      Leaf Sheath Pubescence (Rate on scale from 1 = none to 9 = like              peach fuzz)     6.3      Marginal Waves (Rate on scale from 1 = none to 9 = many)     7.3      Longitudinal Creases (Rate on scale from 1 = none to 9 = many)     5. TASSEL:                     Standard                                         Sample                                    Deviation                                         Size     09.1     Number of Primary Lateral Branches                                    1.61 30     058.7    Branch Angle from Central Spike                                    14.58                                         6     53.2  cm Tassel Length (from top leaf collar to tassel tip)                                    4.07 4     6.5      Pollen Shed (rate on scale from 0 = male sterile to 9 = heavy              shed)     14       Anther Color                    Red     (Munsell code)                                       2.5R 4/8     17       Flume Color                    Purple  (Munsell code)                                       10RP 2/8     1.0      Bar Flumes (Glume Bands): 1 = Absent 2 = Present     22       Peduncle Length (cm. from top leaf to basal branches)     6a. EAR (Unhusked Data):     14  Silk Color (3 days after emergence)                                   Red   (Munsell code)                                                5R36     1   Fresh Husk Color (25 days after 50% silking)                                   Light Green                                         (Munsell code)                                                5GY78     21  Dry Husk Color (65 days after 50% silking)                                    Buff (Munsell code)                                                2.5Y854         Position of Ear at Dry Husk Stage: 1 = Upright 2 = Horizontal 3 =         Pendant     5   Husk Tightness (Rate of Scale from 1 = very loose to 9 = very tight)     2   Husk Extension (at harvest): 1 = Short (ears exposed) 2 = Medium (<8         cm)         3 = Long (8-10 cm beyond ear tip) 4 = Very Long (>10                                                Medium     6b. EAR (Husked Ear Data):     Standard                                         Sample                                    Deviation                                         Size     15    cm Ear Length            0.80 30     41    mm Ear Diameter at mid-point                                    2.23 30     107   gm Ear Weight            21.38                                         30     16       Number of Kernel Rows 0.72 30     2        Kernel Rows: 1 = Indistinct 2 = Distinct                                             Distinct              Row Alignment: 1 = Straight 2 = Slightly Curved 3                                             Straight     1        Row Alignment: 1 = Straight 2 = Slightly Curved 3                                             Straight     16    cm Shank Length          4.36 30              Ear Taper: 1 = Slight 2 = Average 3 = Extreme                                             Extreme     3        Ear Taper: 1 = Slight 2 = Average 3 = Extreme                                             Extreme     7. KERNEL (Dried):             Standard                                         Sample                                    Deviation                                         Size     10    mm Kernel Length         0.72 30     8     mm Kernel Width          0.44 30     4     mm Kernel Thickness      0.50 30     28       % Round Kernels (Shape Grade)                                    8.23 6     1        Aleurone Color Pattern: 1 = Homozygous 2 = Segregating                                             Homozygous     7        Aluerone Color                        Yellow      (Munsell code)                                             2.5Y812     7        Hard Endosperm Color                        Yellow      (Munsell code)                                             2.5Y812     3        Endosperm Type:                        Normal Starch              1 = Sweet (Su1) 2 = Extra Sweet (sh2) 3 = Normal Starch              4 = High Amylose Starch 5 = Waxy Starch 6 = High Protein              7 = High Lysine 8 = Super Sweet (se) 9 = High Oil              10 = Other.sub.----------     24    gm Weight per 100 Kernels (unsized sample)                                    3.44 6     8. COB:                        Standard                                         Sample                                    Deviation                                         Size     24    mm Cob Diameter at mid-point                                    1.89 30     14       Cob Color                    Red             (Munsell code)                                             10R 4/6     2        Cob Strength 1 = Weak 2 = Strong     9. DISEASE RESISTANCE                  (Rate from 1 (most susceptible) to 9 (most resistant); leave                  blank                  if not tested; leave Race or Strain Options blank if                  polygenic):     A. Leaf Blights, Wilts, and Local Infection Diseases            Anthracnose Leaf Blight (Colletotrichum graminicola)     5      Common Rust (Puccinia sorghi)            Common Smut (Ustilago     4      Eyespot (Kabatiella zeae) maydis)     5      Goss's Wilt (Clavibacter michiganense spp. nebraskense)     3      Gray Leaf Spot (Cercospora zeae-maydis)            Helminthosporium Leaf Spot (Bipolaris zeicola) Race.sub.----------            1     3      Northern Leaf Blight (Exserohilum turcicum) Race.sub.----------            Southern Leaf Blight (Bipolaris maydis) Race.sub.----------            Southern Rust (Puccinia polysora)     4      Stewart's Wilt (Erwinia stewartii)            Other (Specify).sub.----------     B. Systemic Diseases            Corn Lethal Necrosis (MCMV and MDMV)            Head Smut (Sphacelotheca reiliana)            Maize Chlorotic Dwarf virus (MDV)            Maize Chlorotic Mottle Virus (MCMV)            Maize Dwarf Mosaic Virus (MDMV)            Sorghum Downy Mildew of Corn (Peronosclerospora sorghi)            Other (Specify).sub.----------     C. Stalk Rots            Anthracnose Stalk Rot (Colletotrichum graminicola)            Dipiodia Stalk Rot (Stenocarpella maydis)            Fusarium Stalk Rot (Fusarium moniliforme)            Gibberella Stalk Rot (Gibberella zeae)            Other (Specify).sub.----------     D. Ear and Kernel Rots            Aspergillus Ear and Kernel Rot (Aspergillus flavus)            Diplodia Ear Rot (Stenocarpella maydis)     4      Fusarium Ear and Kernel Rot (Fusarium moniliforme)     5      Gibberella Ear Rot (Gibberella zeae)            Other (Specify).sub.----------            Banks grass Mite (Oligonychus pratensis)            Corn Worm (Helicoverpa zea)             Leaf Feeding             Silk Feeding              mg larval wt.            Ear Damage            Corn Leaf Aphid (Rhopalosiphum maidis)            Corn Sap Beetle (Carpophilus dimidiatus            European Corn Borer (Ostrinia nubitalis)     6      1st Generation (Typically Whorl Leaf Feeding)     6      2nd Generation (Typically Leaf Sheath-Collar Feeding)            Stalk Tunneling            cm tunneled/plant            Fall Armyworm (Spodoptera fruqiperda)             Leaf Feeding             Silk Feeding             mg larval wt.            Maize Weevil (Sitophilus zeamaize            Northern Rootworm (Diabrotica barberi)            Southern Rootworm (Diabrotica undecimpunctata)            Southwestern Corn Borer (Diatreaea grandiosella)             Leaf Feeding             Stalk Tunneling            cm tunneled/plant            Two-spotted Spider Mite (Tetranychus urticae)            Western Rootworm (Diabrotica virgifrea virgifera)            Other (Specify).sub.----------     11. AGRONOMIC TRAITS:     3      Staygreen (at 65 days after anthesis) (Rate on a scale from 1 =            worst to            excellent)     0.0    % Dropped Ears (at 65 days after anthesis)            % Pre-anthesis Brittle Snapping            % Pre-antheses Root Lodging     39.0   Post-anthesis Root Lodging (at 65 days after anthesis)     5,320  Kg/ha Yield (at 12-13% grain moisture)     __________________________________________________________________________      *In interpreting the foregoing color designations, reference may be had t      the Munsell Glossy Book of Color, a standard color reference.

INDUSTRIAL APPLICABILITY

This invention also is directed to methods for producing a maize plant by crossing a first parent maize plant with a second parent maize plant wherein either the first or second parent maize plant is an inbred maize plant of the line PHDN7. Further, both first and second parent maize plants can come from the inbred maize line PHDN7. Thus, any such methods using the inbred maize line PHDN7 are part of this invention: selfing, backcrosses, hybrid production, crosses to populations, and the like. All plants produced using inbred maize line PHDN7 as a parent are within the scope of this invention. Advantageously, the inbred maize line is used in crosses with other, different, maize inbreds to produce first generation (F₁) maize hybrid seeds and plants with superior characteristics.

As used herein, the term plant includes plant cells, plant protoplasts, plant cell tissue cultures from which maize plants can be regenerated, plant calli, plant clumps, and plant cells that are intact in plants or parts of plants, such as embryos, pollen, ovules, flowers, kernels, ears, cobs, leaves, husks, stalks, roots, root tips, anthers, silk and the like.

Duncan, Williams, Zehr, and Widholm, Planta (1985) 165:322-332 reflects that 97% of the plants cultured that produced callus were capable of plant regeneration. Subsequent experiments with both inbreds and hybrids produced 91% regenerable callus that produced plants. In a further study in 1988, Songstad, Duncan & Widholm in Plant Cell Reports (1988), 7:262-265 reports several media additions that enhance regenerability of callus of two inbred lines. Other published reports also indicated that "nontraditional" tissues are capable of producing somatic embryogenesis and plant regeneration. K. P. Rao, et al., Maize Genetics Cooperation Newsletter, 60:64-65 (1986), refers to somatic embryogenesis from glume callus cultures and B. V. Conger, et al., Plant Cell Reports, 6:345-347 (1987) indicates somatic embryogenesis from the tissue cultures of maize leaf segments. Thus, it is clear from the literature that the state of the art is such that these methods of obtaining plants are, and were, "conventional" in the sense that they are routinely used and have a very high rate of success.

Tissue culture of maize is described in European Patent Application, publication 160,390, incorporated herein by reference. Maize tissue culture procedures are also described in Green and Rhodes, "Plant Regeneration in Tissue Culture of Maize," Maize for Biological Research (Plant Molecular Biology Association, Charlottesville, Va. 1982, at 367-372) and in Duncan, et al., "The Production of Callus Capable of Plant Regeneration from Immature Embryos of Numerous Zea Mays Genotypes," 165 Planta 322-332 (1985). Thus, another aspect of this invention is to provide cells which upon growth and differentiation produce maize plants having the physiological and morphological characteristics of inbred line PHDN7.

Maize is used as human food, livestock feed, and as raw material in industry. The food uses of maize, in addition to human consumption of maize kernels, include both products of dry- and wet-milling industries. The principal products of maize dry milling are grits, meal and flour. The maize wet-milling industry can provide maize starch, maize syrups, and dextrose for food use. Maize oil is recovered from maize germ, which is a by-product of both dry- and wet-milling industries.

Maize, including both grain and non-grain portions of the plant, is also used extensively as livestock feed, primarily for beef cattle, dairy cattle, hogs, and poultry.

Industrial uses of maize include production of ethanol, maize starch in the wet-milling industry and maize flour in the dry-milling industry. The industrial applications of maize starch and flour are based on functional properties, such as viscosity, film formation, adhesive properties, and ability to suspend particles. The maize starch and flour have application in the paper and textile industries. Other industrial uses include applications in adhesives, building materials, foundry binders, laundry starches, explosives, oil-well muds, and other mining applications.

Plant parts other than the grain of maize are also used in industry: for example, stalks and husks are made into paper and wallboard and cobs are used for fuel and to make charcoal.

The seed of inbred maize line PHDN7, the plant produced from the inbred seed, the hybrid maize plant produced from the crossing of the inbred, hybrid seed, and various parts of the hybrid maize plant can be utilized for human food, livestock feed, and as a raw material in industry.

PERFORMANCE EXAMPLES OF PHDN7

In the examples that follow, the traits and characteristics of inbred maize line PHDN7 are presented as an inbred per se and in hybrid combination. The data collected on inbred maize line PHDN7 is presented for key characteristics and traits.

Inbred Comparisons

The results in Table 2A compare inbred PHDN7 to inbred PHBF0. The inbred per se results show inbred PHDN7 has above average yield and yields better than PHBF0. Inbred PHDN7 also has lower harvest moisture and better test weight than inbred PHBF0. Inbred PHDN7 flowers significantly earlier (GDU Shed and GDU Silk) than inbred PHBF0, has significantly better seedling vigor and significantly better early stand count than inbred PHBF0. Inbred PHDN7 has significantly greater pollen weight and larger tassel size than inbred PHBF0.

The results in Table 2B compare inbred PHDN7 to inbred PHFR8. Both inbreds have above average yield, with inbred PHDN7 having significantly lower harvest moisture than inbred PHFR8. Inbred PHDN7 sheds pollen significantly earlier (GDU to Shed) than inbred PHFR8. Inbred PHDN7 has significantly better seedling vigor and a significantly better early stand count than inbred PHFR8. Inbred PHDN7 has significantly larger tassel size than inbred PHFR8 and both inbreds have greater than average pollen weight.

The results in Table 2C compare inbred PHDN7 to inbred PH54B. The inbred per se results show that inbred PHDN7 has above average yield and yields significantly better than PH54B. Inbred PHDN7 has significantly greater pollen weight and significantly larger tassel size and ear size than inbred PH54B.

Inbred by Tester Comparisons

The results in Table 3 compare the inbred PHDN7 and inbred PHFR8, when each inbred is crossed to the same tester lines. Both the PHDN7 and the PHFR8 hybrids have above average yields and the PHDN7 hybrids have significantly lower harvest moisture than the PHFR8 hybrids. The PH0HC hybrids demonstrate significantly better seedling vigor and significantly earlier pollen shed (GDU to Shed) than the PHFR8 hybrids.

Hybrid Comparisons

The results in Table 4A compare inbred PH22G crossed to PHDN7 and inbred PHDP0 crossed to PHJ89. The results show that both hybrids have above average yields. The PH22G/PHDN7 hybrid has significantly lower harvest moisture than the PHDP0/PHJ89 hybrid. Both hybrids have above average seedling vigor. The PH22G/PHDN7 hybrid has a significantly earlier flowering (GDU Shed and GDU Silk) than the PHDP0/PHJ89 hybrid.

The results in Table 4B compare inbred PH22G crossed to PHDN7 and inbred PHAA0 crossed to PHBF0. The results show that both hybrids have above average yields. The PH22G/PHDN7 hybrid has lower harvest moisture and significantly higher test weight than the PHAA0/PHBF0 hybrid. Both hybrids have above average seedling vigor. The PH22G/PHDN7 hybrid shows a significantly earlier silk emergence (GDU to Silk) than the PHAA0/PHBF0 hybrid.

                                      TABLE 2A     __________________________________________________________________________     PAIRED INBRED COMPARISON REPORT     VARIETY #1 = PHDN7     VARIETY #2 = PHBF0     __________________________________________________________________________                BU   BU        TST  SDG  EST  TIL  GDU  GDU                ACR  ACR  MST  WT   VGR  CNT  LER  SHD  SLK                ABS  % MN ABS  ABS  ABS  ABS  ABS  ABS  ABS     __________________________________________________________________________     TOTAL SUM            1   106.1                     122  18.3 53.9 6.2  34.5 2.2  118.8                                                        120.8            2   85.8 99   19.3 52.7 4.3  27.6 2.5  123.4                                                        126.3            LOCS                10   10   14   9    42   81   66   112  109            REPS                17   17   21   16   44   122  74   119  114            DIFF                20.3 23   1.0  1.2  1.9  6.9  0.2  4.6  5.5            PR > T                .021+                     .023+                          .089*                               .029+                                    .000#                                         .000#                                              .743 .000#                                                        .000#     __________________________________________________________________________                POL  POL  POL  TAS  TAS  PLT  EAR  RT   STA                WT   WT   SC   BLS  SZ   HT   HT   LDG  GRN                ABS  % MN ABS  ABS  ABS  ABS  ABS  ABS  ABS     __________________________________________________________________________     TOTAL SUM            1   165.6                     138  5.6  8.0  6.0  89.6 36.5 46.8 3.6            2   95.7 82   5.4  8.8  5.5  79.8 35.4 85.3 3.8            LOCS                13   13   27   4    47   59   51   10   5            REPS                14   14   27   4    49   65   56   11   5            DIFF                69.9 57   0.2  0.8  0.5  9.8  1.1  38.5 0.2            PR > T                .002#                     .002#                          .593 .215 .033+                                         .000#                                              .120 .003#                                                        .374     __________________________________________________________________________                STK  BRT  GRN  SCT  EAR  TEX  EAR  BAR  DRP                LDG  STK  APP  GRN  SZ   EAR  MLD  PLT  EAR                ABS  ABS  ABS  ABS  ABS  ABS  ABS  ABS  ABS     __________________________________________________________________________     TOTAL SUM            1   96.7 100.0                          5.8  7.0  5.6  2.7  6.4  98.9 100.0            2   95.2 98.9 5.6  7.0  5.4  2.9  6.2  98.1 100.0            LOCS                7    7    4    22   5    7    25   29   5            REPS                10   7    6    24   5    7    29   31   8            DIFF                1.5  1.1  0.1  0.0  0.2  0.1  0.1  0.8  0.0            PR > T                .395 .356 .718 .999 .704 .838 .641 .420 .999     __________________________________________________________________________                GLF  NLF  GOS  STW  HD   FUS  GIB  EYE  COM                SPT  BLT  WLT  WLT  SMT  ERS  ERS  SPT  RST                ABS  ABS  ABS  ABS  ABS  ABS  ABS  ABS  ABS     __________________________________________________________________________     TOTAL SUM            1   3.3  3.1  5.6  4.0  92.3 4.5  4.0  3.5  4.5            2   3.5  2.8  6.3  6.0  85.1 6.0  6.8  3.7  3.5            LOCS                2    11   4    1    9    1    3    3    2            REPS                4    19   8    2    24   2    6    5    2            DIFF                0.3  0.3  0.6  2.0  7.3  1.5  2.8  0.2  1.0            PR > T                .500 .308 .194      .047+     .060*                                                   .742 .500     __________________________________________________________________________                                             HC  ECB ECB ECB                                             BLT DPE 1LF 2SC                                             ABS ABS ABS ABS     __________________________________________________________________________                                TOTAL SUM                                        1    6.3 87.5                                                     6.6 5.9                                        2    6.3 93.8                                                     6.3 5.6                                        LOCS 1   1   8   4                                        REPS 3   2   11  8                                        DIFF 0.0 6.3 0.4 0.3                                        PR > T       .170                                                         .789     __________________________________________________________________________      * = 10% SIG      + = 5% SIG      # = 1% SIG

                                      TABLE 2B     __________________________________________________________________________     PAIRED INBRED COMPARISON REPORT     VARIETY #1 = PHDN7     VARIETY #2 = PHFR8     __________________________________________________________________________                BU   BU        TST  SDG  EST  TIL  GDU  GDU                ACR  ACR  MST  WT   VGR  CNT  LER  SHD  SLK                ABS  % MN ABS  ABS  ABS  ABS  ABS  ABS  ABS     __________________________________________________________________________     TOTAL SUM            1   91.7 115  19.3 53.0 6.3  40.5 1.9  119.4                                                        121.2            2   91.4 115  20.7 55.1 5.1  38.0 2.7  121.2                                                        121.6            LOCS                37   37   42   28   56   113  91   144  138            REPS                73   73   77   56   64   178  112  159  148            DIFF                0.3  0    1.4  2.1  1.2  2.4  0.9  1.8  0.4            PR > T                .908 .999 .000#                               .000#                                    .000#                                         .007#                                              .136 .000#                                                        .397     __________________________________________________________________________                POL  POL  POL  TAS  TAS  PLT  EAR  RT   STA                WT   WT   SC   BLS  SZ   HT   HT   LDG  GRN                ABS  % MN ABS  ABS  ABS  ABS  ABS  ABS  ABS     __________________________________________________________________________     TOTAL SUM            1   133.7                     121  5.6  8.0  5.9  87.4 35.5 63.5 3.8            2   122.2                     112  5.4  8.8  5.3  73.8 29.5 90.9 5.0            LOCS                10   10   40   5    53   81   73   14   13            REPS                12   12   45   6    56   97   88   20   18            DIFF                11.5 10   0.2  0.8  0.5  13.6 6.0  27.4 1.2            PR > T                .381 .416 .386 .227 .004#                                         .000#                                              .000#                                                   .003#                                                        .003#     __________________________________________________________________________                STK  BRT  GRN  SCT  EAR  TEX  EAR  BAR  DRP                LDG  STK  APP  GRN  SZ   EAR  MLD  PLT  EAR                ABS  ABS  ABS  ABS  ABS  ABS  ABS  ABS  ABS     __________________________________________________________________________     TOTAL SUM            1   97.2 99.9 5.7  7.1  5.6  2.9  6.4  97.3 99.7            2   97.6 100.0                          6.5  7.7  4.8  4.2  6.9  97.6 99.9            LOCS                24   9    15   24   5    8    28   39   18            REPS                46   11   30   26   5    9    32   4.7  36            DIFF                0.5  0.1  0.9  0.6  0.8  1.3  0.5  0.3  0.2            PR > T                .686 .347 .000#                               .005#                                    .099*                                         .006#                                              .211 .476 .345     __________________________________________________________________________                GLF  NLF  GOS  STW  HD   FUS  GIB  EYE  COM                SPT  BLT  WLT  WLT  SMT  ERS  ERS  SPT  RST                ABS  ABS  ABS  ABS  ABS  ABS  ABS  ABS  ABS     __________________________________________________________________________     TOTAL SUM            1   3.0  3.2  5.0  4.0  89.1 4.3  4.7  3.5  4.8            2   5.5  2.7  5.5  4.5  71.7 3.8  5.2  3.7  5.4            LOCS                1    9    3    1    6    2    5    3    4            REPS                2    16   5    2    12   3    10   5    6            DIFF                2.5  0.5  0.5  0.5  17.4 0.5  0.5  0.2  0.6            PR > T   .076*                          .225      .047+                                         .500 .537 .874 .194     __________________________________________________________________________                                             HC  ECB ECB ECB                                             BLT DPE 1LF 2SC                                             ABS ABS ABS ABS     __________________________________________________________________________                                TOTAL SUM                                        1    6.3 87.5                                                     6.8 5.9                                        2    8.0 100.0                                                     6.7 5.9                                        LOCS 1   1   7   5                                        REPS 3   2   12  10                                        DIFF 1.7 12.5                                                     0.1 0.0                                        PR > T       .829                                                         .999     __________________________________________________________________________      * = 10% SIG      + = 5% SIG      # = 1% SIG

                                      TABLE 2C     __________________________________________________________________________     PAIRED INBRED COMPARISON REPORT     VARIETY #1 = PHDN7     VARIETY #2 = PH54B     __________________________________________________________________________                BU   BU        TST  SDG  EST  TIL  GDU  GDU                ACR  ACR  MST  WT   VGR  CNT  LER  SHD  SLK                ABS  % MN ABS  ABS  ABS  ABS  ABS  ABS  ABS     __________________________________________________________________________     TOTAL SUM            1   94.5 124  17.4 55.4 6.0  39.0 1.5  119.8                                                        121.6            2   65.6 85   15.7 56.6 5.7  38.5 1.4  114.2                                                        116.6            LOCS                13   13   17   13   50   94   73   118  116            REPS                26   26   30   26   57   153  93   133  129            DIFF                28.9 38   1.7  1.2  0.3  0.5  0.1  5.6  5.0            PR > T                .000#                     .000#                          .003#                               .048+                                    .158 .265 .853 .000#                                                        .000#     __________________________________________________________________________                POL  POL  POL  TAS  TAS  PLT  EAR  RT   STA                WT   WT   SC   BLS  SZ   HT   HT   LDG  GRN                ABS  % MN ABS  ABS  ABS  ABS  ABS  ABS  ABS     __________________________________________________________________________     TOTAL SUM            1   163.6                     135  5.9  8.2  6.0  82.3 33.6 55.1 3.5            2   87.9 73   5.4  9.0  5.0  77.7 30.7 41.9 2.5            LOCS                20   20   27   6    40   62   55   10   11            REPS                26   26   32   8    42   72   64   11   15            DIFF                75.6 62   0.5  0.8  0.9  4.6  2.8  13.2 0.9            PR > T                .000#                     .000#                          .121 .141 .000#                                         .000#                                              .000#                                                   .167 .043+     __________________________________________________________________________                STK  BRT  GRN  SCT  EAR  TEX  EAR  BAR  DRP                LDG  STK  APP  GRN  SZ   EAR  MLD  PLT  EAR                ABS  ABS  ABS  ABS  ABS  ABS  ABS  ABS  ABS     __________________________________________________________________________     TOTAL SUM            1   95.5 100.0                          5.9  7.0  6.5  2.5  6.3  96.8 99.4            2   96.6 100.0                          5.4  6.1  5.5  2.5  5.6  95.8 97.8            LOCS                11   4    8    14   2    4    19   30   9            REPS                20   4    16   16   2    4    22   34   18            DIFF                1.1  0.0  0.6  0.9  1.0  0.0  0.7  1.0  1.6            PR > T                .225 .999 .357 .060*                                    .000#                                         .999 .031+                                                   .317 .095*     __________________________________________________________________________                                   GLF                                      NLF GOS                                             STW                                                HD  GIB                                                       ECB                                                          ECB                                   SPT                                      BLT WLT                                             WLT                                                SMT ERS                                                       1LF                                                          2SC                                   ABS                                      ABS ABS                                             ABS                                                ABS ABS                                                       ABS                                                          ABS     __________________________________________________________________________                        TOTAL SUM                               1   3.0                                      3.3 5.7                                             4.0                                                91.8                                                    5.3                                                       5.5                                                          6.0                               2   3.5                                      2.5 7.0                                             5.5                                                98.8                                                    5.5                                                       3.0                                                          3.5                               LOCS                                   1  5   3  1  5   2  2  1                               REPS                                   2  7   6  2  12  4  2  2                               DIFF                                   0.5                                      0.8 1.3                                             1.5                                                7.0 0.3                                                       2.5                                                          2.5                               PR > T .078*                                          .251  .052*                                                    .795                                                       .344     __________________________________________________________________________      * = 10% SIG      + = 5% SIG      # = 1% SIG

                                      TABLE 3     __________________________________________________________________________     Average Inbred By Tester Performance Comparing PHDN7 To PHFR8 Crossed     To The Same Inbred Testers And Grown In The Same Experiments.     __________________________________________________________________________                SEL     BU  BU  PRM     TST SDG EST GDU                IND PRM ACR ACR SHD MST WT  VGR CNT SHD                % MN                    ABS ABS % MN                                ABS % MN                                        ABS % MN                                                % MN                                                    % MN     __________________________________________________________________________     TOTAL SUM            REPS                32  42  139 139 23  313 92  276 210 122            LOCS                32  42  116 116 23  262 72  213 162 90            PHDN7                103 88  144 103 90  97  54  104 99  99            PHFR8                103 89  143 102 91  99  54  92  100 101            DIFF                0   1   1   1   1   2   0   11  0   1            PR > T                0.99                    0.01                        0.58                            0.35                                0.01                                    0.00                                        0.99                                            0.00                                                0.99                                                    0.00     __________________________________________________________________________                GDU STK PLT EAR RT  STA STK BRT GRN HD                SLK CNT HT  HT  LDG GRN LDG STK APP SMT                % MN                    % MN                        % MN                            % MN                                % MN                                    % MN                                        % MN                                            % MN                                                % MN                                                    ABS     __________________________________________________________________________     TOTAL SUM            REPS                102 441 72  72  171 118 186 29  33  1            LOCS                81  354 59  59  131 97  149 24  30  1            PHDN7                100 100 103 104 93  90  101 102 98  100            PHFR8                100 101 97  93  103 121 102 100 97  100            DIFF                1   0   5   11  9   31  1   2   1   0            PR > T                0.13                    0.99                        0.00                            0.00                                0.00                                    0.00                                        0.22                                            0.43                                                0.83                                                    0.99     __________________________________________________________________________                                        EYE                                           ECB                                              ECB                                                 DRP NLF                                        SPT                                           DPE                                              2SC                                                 EAR BLT                                        ABS                                           ABS                                              ABS                                                 % MN                                                     ABS     __________________________________________________________________________                             TOTAL SUM                                    REPS                                        1  2  2  63  8                                    LOCS                                        1  1  1  58  4                                    PHDN7                                        4  100                                              4  100 5                                    PHFR8                                        8  99 5  100 5                                    DIFF                                        4  1  1  0   0                                    PR > T       0.99                                                     0.99     __________________________________________________________________________      *PR > T values are valid only for comparisons with Locs >= 10.

                                      TABLE 4A     __________________________________________________________________________     INBREDS IN HYBRID COMBINATION REPORT     VARIETY #1 = PH22G/PHDN7     VARIETY #2 = PHDP0/PHJ89     __________________________________________________________________________                     PRM  BU   BU        TST  SDG  EST  GDU                PRM  SHD  ACR  ACR  MST  WT   VGR  CNT  SHD                ABS  ABS  ABS  % MN % MN ABS  % MN % MN % MN     __________________________________________________________________________     TOTAL SUM            1   93   92   145.9                               104  96   54.3 109  101  97            2   96   99   149.3                               106  102  54.8 108  105  402            LOCS                16   14   41   41   42   26   37   37   20            REPS                16   14   57   57   58   38   50   47   30            DIFF                3    7    3.4  2    6    0.5  0    4    5            PR > T                .000#                     .000#                          .247 .342 .000#                                         .051*                                              .999 .115 .000#     __________________________________________________________________________                GDU  STK  PLT  EAR  RT   STA  STK  BRT  DRP                SLK  CNT  HT   HT   LDG  GPN  LDG  STK  EAR                % MN % MN % MN % MN % MN % MN % MN % MN % MN     __________________________________________________________________________     TOTAL SUM            1   96   100  99   107  91   80   102  120  100            2   102  102  101  98   98   100  101  104  100            LOCS                17   76   30   30   19   27   38   10   32            REPS                23   129  51   51   28   41   52   15   41            DIFF                6    2    2    9    7    20   1    17   0            PR > T                .000#                     .013+                          .002#                               .000#                                    .052*                                         .010+                                              .650 .068*                                                        .999     __________________________________________________________________________                                  NLF  GOS  HD   GIB                                                    EYE                                                       ECB                                                          ECB                                  BLT  WLT  SMT  ERS                                                    SPT                                                       1LF                                                          2SC                                  ABS  ABS  ABS  ABS                                                    ABS                                                       ABS                                                          ABS     __________________________________________________________________________                       TOTAL SUM                              1   4.7  5.8  100.0                                                 6.5                                                    7.5                                                       3.6                                                          5.5                              2   7.0  7.5  92.0 6.8                                                    8.0                                                       5.0                                                          5.1                              LOCS                                  3    2    2    4  2  5  7                              REPS                                  6    4    6    8  2  5  9                              DIFF                                  2.3  1.8  8.0  0.3                                                    0.5                                                       1.4                                                          0.4                              PR > T                                  .034+                                       .090*                                            .390 .604                                                    .500                                                       .108                                                          .634     __________________________________________________________________________      * = 10% SIG      + = 5% SIG      # = 1% SIG

                                      TABLE 4B     __________________________________________________________________________     INBREDS IN HYBRID COMBINATION REPORT     VARIETY #1 = PH22G/PHDN7     VARIETY #2 = PHAA0/PHBF0     __________________________________________________________________________                     PRM  BU   BU        TST  SDG  EST  GDU                PRM  SHD  ACR  ACR  MST  WT   VGR  CNT  SHD                ABS  ABS  ABS  % MN % MN ABS  % MN % MN % MN     __________________________________________________________________________     TOTAL SUM            1   91   93   149.3                               106  96   53.0 104  98   100            2   92   92   149.4                               106  98   52.3 104  97   99            LOCS                18   22   67   67   68   32   55   50   41            REPS                18   22   108  108  109  50   89   72   68            DIFF                1    1    0.2  0    1    0.7  0    1    1            PR > T                .221 .200 .938 .999 .080*                                         .000#                                              .999 .469 .045+     __________________________________________________________________________                GDU  STK  PLT  EAR  RT   STA  STK  BRT  DRP                SLK  CNT  HT   HT   LDG  GRN  LDG  STK  EAR                % MN % MN % MN % MN % MN % MN % MN % MN % MN     __________________________________________________________________________     TOTAL SUM            1   97   99   102  110  94   94   102  116  100            2   99   99   99   101  94   101  100  108  100            LOCS                21   110  39   39   35   25   69   16   25            REPS                32   192  67   67   54   39   111  22   34            DIFF                2    1    3    9    0    7    2    8    0            PR > T                .009#                     .185 .000#                               .000#                                    .999 .331 .145 .024+                                                        .999     __________________________________________________________________________                            NLF GOS HD   GIB EYE ECB ECB ECB                            BLT WLT SMT  ERS SPT DPE 1LF 2SC                            ABS ABS ABS  ABS ABS ABS ABS ABS     __________________________________________________________________________                 TOTAL SUM                        1   4.8 5.8 100.0                                         6.5 6.6 97.1                                                     3.6 5.0                        2   3.8 7.5 93.2 5.4 6.6 96.2                                                     4.0 5.0                        LOCS                            2   2   2    4   4   13  5   5                        REPS                            4   4   6    8   6   26  5   5                        DIFF                            1.0 1.8 6.8  1.1 0.0 0.9 0.4 0.0                        PR > T                            .295                                .090*                                    .500 .319                                             .999                                                 .204                                                     .374                                                         .999     __________________________________________________________________________      * = 10% SIG      + = 5% SIG      # = 1% SIG

Applicant has made a deposit of at least 2500 seeds of Inbred Maize Line PHDN7 with the American Type Culture Collection (ATCC), Manassas, Va. 20110 USA, ATCC Deposit No. 203512. The seeds deposited with the ATCC on Dec. 8, 1998 were taken from the deposit maintained by Pioneer Hi-Bred International, Inc., 800 Capital Square, 400 Locust Street, Des Moines, Iowa 50309-2340 since prior to the filing date of this application. This deposit of the Inbred Maize Line PHDN7 will be maintained in the ATCC depository, which is a public depository, for a period of 30 years, or 5 years after the most recent request, or for the effective life of the patent. whichever is longer, and will be replaced if it becomes nonviable during that period. Additionally, Applicant has satisfied all the requirements of 37 C.F.R. §§1.801-1.809, including providing an indication of the viability of the sample. Applicant imposes no restrictions on the availability of the deposited material from the ATCC; however, Applicant has no authority to waive any restrictions imposed by law on the transfer of biological material or its transportation in commerce Applicant does not waive any infringement of its rights granted under this patent or under the Plant Variety Protection Act (7 USC 2321 et seq.). U.S. Plant Variety Protection of PHBN7 has been applied for under Application No. 9700197.

The foregoing invention has been described in detail by way of illustration and example for purposes of clarity and understanding. However, it will be obvious that certain changes and modifications such as single gene modifications and mutations, somoclonal variants, variant individuals selected from large populations of the plants of the instant inbred and the like may be practiced within the scope of the invention, as limited only by the scope of the appended claims. 

What is claimed is:
 1. Seed of maize inbred line designated PHDN7, representative samples having been deposited under ATCC Accession No.
 203512. 2. A maize plant or parts thereof, of inbred Line PHDN7, seed of said line having been deposited under ATCC accession No.
 203512. 3. The maize plant of claim 2, wherein said plant is male sterile.
 4. A tissue culture of regenerable cells of a maize plant of inbred line PHDN7, wherein said tissue culture regenerates plants capable of expressing all the morphological and physiological characteristics of the inbred line PHDN7, representative seed of which have been deposited under ATCC Accession No.
 203512. 5. A tissue culture according to claim 4, wherein the regenerable cells are cells or protoplasts being of a tissue selected from the group consisting of leaves, pollen, embryos, roots, root tips, anthers, silks, flowers, kernels, ears, cobs, husks, and stalks.
 6. A maize plant regenerated from the tissue culture of claim 4, said plant capable of expressing all the morphological and physiological characteristics of inbred line PHDN7, representative seed of which have been deposited under ATCC Accession No.
 203512. 7. A method for producing a first generation (F₁) hybrid maize seed comprising crossing the plant of claim 2 with a different inbred parent maize plant and harvesting the resultant first generation (F₁) hybrid maize seed.
 8. The method of claim 7 wherein inbred maize plant of claim 2 is the female or male parent.
 9. An F₁ hybrid seed produced by crossing the inbred maize plant according to claim 2 with another, different maize plant.
 10. An F₁ hybrid plant, or parts thereof, grown from the seed of claim
 9. 11. A process for producing inbred line PHDN7, seed of said line having been deposited under ATCC accession No. 203512, comprising:planting a collection of seed comprising seed of a hybrid, one of whose parents is inbred PHDN7 said collection also comprising seed of said inbred; growing plants from said collection of seed; identifying said inbred plants; selecting said inbred plant; and controlling pollination in a manner which preserves the homozygosity of said inbred plant.
 12. The process of claim 11 wherein said step of identifying said inbred plant comprises:identifying plants with decreased vigor.
 13. The process of claim 11 wherein said step of identifying said inbred plant comprises:identifying seeds or plants with homozygous genotype.
 14. A maize plant, or parts thereof, having all the physiological and morphological characteristics of the plant of claim
 2. 15. A male sterile maize plant, or parts thereof, otherwise having all the physiological and morphological characteristics of the plant of claim
 2. 16. A method for producing a first generation (F₁) hybrid maize seed comprising crossing the plant of claim 14 with a different inbred maize plant and harvesting the resultant first generation (F₁) hybrid maize seed.
 17. The method of claim 16 wherein said maize plant of claim 14 is the female or male parent.
 18. An F₁ hybrid seed produced by crossing the inbred maize plant according to claim 14 with another, different maize plant.
 19. An F₁ hybrid plant, or parts thereof, grown from the seed of claim
 18. 